1. Field of the Invention
This invention relates to the winding of filamentary material in a figure 8 configuration with a radial payout hole extending from the inside to the outside of the wind, and more particularly to such winding in which a uniform radial payout hole is produced regardless of the diameter or thickness of the wind.
2. Related Art
Method and apparatus for producing a figure 8 wind with a radial payout hole extending through the wall of the wind is disclosed in U.S. Pat. No. 4,406,419, entitled: "Method and Apparatus for Winding Flexible Material" and assigned to the same assignee as the subject application. The winding techniques disclosed in the aforesaid patent are used by the assignee, Windings, Inc., along with other winding techniques, to produce winds of the aforementioned kind in accordance with the REELEX system, which is licensed in the United States and foreign countries.
In accordance with the currently used REELEX system a coil of filamentary material is wound on a mandrel 20 having a radius r.sub.2, and with a radial payout hole in the form of a wedge 22 of essentially constant angle A along the radius of the wind 24, as shown in FIG. 1. It is evident that the generation of a payout hole 22 using a constant angle A results in an increasing circumferential distance in direct proportion to the radius of the wind. This difference in circumferential distance is evident from a consideration of a wind having a radius r.sub.1 which results in the distance B being subtended as, for example, by the radius r.sub.2 of the mandrel itself (in effect a zero radius wind) which subtends a distance C. Thus if the coil is wound with an initial size of the payout hole 22 equal to allow a payout tube to be inserted therein after the wind is completed, it is apparent that the size of the payout hole 22 will be too large when the wind is finished with a radius of r.sub.1. It is therefore desirable to provide a technique for modifying or adjusting the size of the payout hole during the winding of a coil, and especially for larger diameter coils where the inner and outer size of the payout holes have greater disparity (for example, compare distances B and C of FIG. 1).
The problems caused by such a payout hole are as follows:
(1) When producing coils in accordance with the REELEX system, a "valley" is generated where there are no crossovers. This causes the coil to become lumpy due to the varying densities of the wound filamentary material. The valleys extend outwardly from the payout hole, around the circumference, and terminate at the sides of the coil 180 degrees from the hole. This causes lumpiness in the surface of the coil, which defect becomes exaggerated as the coil diameter increases and as the hole becomes larger. FIG. 2 shows a coil winding layer laid out flat with the valleys and the payout hole designated as such. PA1 (2) The lumpiness causes slippage of the winds that often obscures the payout hole. To overcome this problem, the hole size is often increased, which makes the problem of slippage worse and also lowers the density of the wind even further. PA1 (3) The package (which is usually, but not always, a box-like container) must be made larger to accommodate the lumps 26, 27 as illustrated in FIG. 4, where it can be seen that if the high points 28 in the wind 30 were not present, the box or container dimension could be smaller if the wind were produced without the high points 28. PA1 (4) Since the payout hole uses up some circumference of the coil, the larger the hole is, the larger the coil will be.
U.S. Pat. No. 4,523,723, entitled: Winding Flexible Material with Layer Shifting and also assigned to Windings, Inc. discloses a method of winding flexible material more densely by varying the speed of the traverse or the speed of the mandrel with respect to one another. The patent also includes Figures with flattened windings similar to that of FIG. 2 herein. However, the techniques disclosed in this patent do not overcome the problem of the wedge-shaped payout hole as defined above.
FIGS. 5a and 5b illustrate the problem of the wasted space 33 produced by a payout hole 32 in a winding 34 made with constant angle as shown in FIG. 5a, and the lack of wasted space produced by a payout hole 35 made in a winding 36 with a constant circumference or diameter as shown in FIG. 5b. In FIG. 5a wasted space 33 is formed between payout tube 37 and the side 38 of the payout hole 32. In FIG. 5b payout tube 40 fits neatly within payout hole 35 formed with substantially parallel sides (constant diameter). The constant width payout hole 35 in FIG. 5b is formed by starting the wind with a given angle and varying the angle as the coil diameter increases. Coil densities can be increased by as much as 7% due to the increase in available circumference. This translates to about 0.5 inch of coil diameter for 18 inch diameter coils. The savings due to the decrease in the package size because of the reduction in the "lumpiness" is even higher.
In order to produce the desired effect of a "constant" hole, the hole must first be straightened. If the hole were allowed to be formed without straightening, the actual formation would look like FIGS. 5c and 5d, which show constant angle, and FIGS. 5e and 5f, which show constant size. The important points that are illustrated in these Figures is that the twisted payout hole forces the payout tube (guide) to lie in some orientation other than along a radial (FIG. 5c). To insure that the payout tube is oriented properly, the payout hole must be made larger. FIGS. 5e and 5f show the same problem, but with less wasted space. In order to receive the full benefit from this process, the payout hole must be straight (along radials) and of constant size.
U.S. Pat. No. 3,747,861, entitled: Apparatus and Method for Winding Flexible Material for Twistless Payout Through a Straight Radial Opening discloses a technique for straightening the payout hole by adjusting the speed of the traverse or mechanically shifting the spindle. In the apparatus of the aforementioned patent, the mechanism that causes the payout to shift in the first instance is the result of the motion of the traverse in a direction away from the spindle shaft and the motion of the traverse away from the spindle shaft and through an arc. This movement causes the payout hole to curve in a direction opposite to that of the rotation of the spindle. Because of the cost and complexity of such bailing techniques, REELEX systems have never employed commercial or industrial winding machines that use such a bailing technique.
In the REELEX system, properly formed endforms and mandrels are used with a traverse that is stationary, i.e. does not move in a direction perpendicular to the shaft of the spindle (for example, see the aforementioned U.S. Pat. No. 4,406,419). When the traverse remains a fixed distance from the spindle shaft axis or mandrel surface, a different situation occurs than when the traverse does not remain a fixed distance from the spindle shaft axis. In the former situation, as the coil is wound, the increase in diameter causes the surface of the coil to move toward the traverse, which has the affect of laying the material down sooner then the preceding layer. This results in a slight positive shift in phase from layer to layer, causing among other things, a tilted payout hole. But in this case the payout hole shifts in the same direction as the spindle rotation. This positive advance from layer to layer as the coil builds in diameter may be counteracted by introducing a product diameter input into the winding microprocessor. The technique uses an algorithm that calculates the theoretical diameter of the coil at each layer (as opposed to actually sensing the diameter), and determines the amount of phase shift that should have occurred. The winding algorithm then causes a corresponding minus shift of the payout hole and the whole layer of the wind. The shift always occurs to the side of the payout hole that the layer is approaching and never to the side of the payout hole that has just occurred.
For minus gain or advance the approach is to the zero side, and for the plus gain or advance it is the NOT HOLE SIZE--360 degrees minus the HOLE SIZE. The resulting straight hole can be reduced in overall size because the payout tube can be inserted straight in and remain in a radial line. Because of this reduction in the constant angle of the hole size, there is a corresponding reduction in the size of the package. This, plus the constant circumference process discussed above, will result in the overall reduction in coil diameters of more than an inch for larger diameter coils, such as 18 inch coils.